The present invention relates generally to the field of grain drying and storage bins and more particularly, to an improved fan mounting arrangement for such a grain drying and storage bin.
Grain drying and storage bins have existed in the prior art for many years. Such bins generally include a concrete base, a side wall forming a generally cylindrical housing of corrugated steel extending upwardly from the base and a roof. Within such housing, a perforated floor is supported in spaced relationship above the concrete base to provide a plenum chamber into which air is forced for circulation to the grain and a grain drying and storage chamber above the perforated floor into which the grain is introduced for drying and storage. Positioned near the bottom of the side wall of the bin about its periphery are a plurality of air circulation means in the form of ventilation and drying fans. In some structures these fans are mounted directly to the bin wall, while in others the fans are mounted separate from the wall with an external transition duct. These fans introduce air into the plenum chamber, the spaced located below the perforated floor, and force it upwardly through the perforated floor and through the grain during the drying process. A plurality of lamps or other source of heat may also be positioned about the periphery of the bin to assist in the drying process.
In the past, fans were mounted either to the side wall of the bin or spaced from the bin such that the entire fan outlet was positioned below the perforated floor. While this was a generally satisfactory mounting arrangement, it tended to result in in adequate and uneven airflow in the grain, particularly in the area near the fans. It was believed that these stagnant areas or areas or uneven airflow were formed as a result of a negative draft being created by the air forced into the plenum chamber past a portion of the underside of the floor, thus actually resulting in a downward flow of air from the grain through the perforated floor in the area of the fans. Another mounting arrangement for a fan in a grain drying and storage bin is to mount the fan such that a portion of the fan outlet is disposed above the perforated floor. Such a mounting arrangement is illustrated in U.S. Pat. No. 4,037,527. It was believed that by positioning a portion of the fan above the floor level, the negative draft situation, and thus the inadequate and uneven airflow in the grain at these locations would be eliminated. While this particular mounting arrangement was considered to be an improvement over the prior method of mounting the fan entirely below the floor level, it created certain additional problems. One of these was the build-up of fan back pressure in the area where the fan was positioned above the floor, thus resulting in fan vibration and reduced life, loosening of bolts, etc. Thus, there is a real need in the art for an improved fan mounting arrangement which eliminates the negative draft situation resulting from air being forced into the plenum chamber and which also eliminates the increased back pressure and fan vibration resulting from mounting a portion of the fan above the perforated floor level.